ACS provides a solution to the scenario as depicted in the following image.

The UserNameWSTrustBinding, CertificateWSTrustBinding, and IssuedTokenWSTrustBinding classes are available as part of the Windows Identity Foundation’s (WIF) Microsoft.IdentityModel.Protocols.WSTrust.Bindings namespace and they are used to request a token from ACS.

Windows Identity Foundation (WIF) is used to validate incoming tokens.

Windows Identity Foundation (WIF) is used to parse the incoming tokens.

Windows Identity Foundation (WIF) is used to implement authorization checks.

The ACS rule engine is used to transform tokens.

Most of the work is done using the configuration either in the application’s web.config or/and through the ACS Management Portal.